org.apache.commons.collections.map
Class AbstractHashedMap

java.lang.Object
  |
  +--org.apache.commons.collections.map.AbstractHashedMap

All Implemented Interfaces:

IterableMap, java.util.Map

Direct Known Subclasses:

AbstractLinkedMap, CaseInsensitiveMap, HashedMap, IdentityMap

public class AbstractHashedMap

extends java.lang.Object

implements IterableMap

An abstract implementation of a hash-based map which provides numerous points for subclasses to override.

This class implements all the features necessary for a subclass hash-based map. Key-value entries are stored in instances of the HashEntry class, which can be overridden and replaced. The iterators can similarly be replaced, without the need to replace the KeySet, EntrySet and Values view classes.

Overridable methods are provided to change the default hashing behaviour, and to change how entries are added to and removed from the map. Hopefully, all you need for unusual subclasses is here.

Since:

Commons Collections 3.0

Version:

$Revision: 1.10 $ $Date: 2004/01/14 21:43:11 $

Author:

java util HashMap, Stephen Colebourne

Method Summary

void	clear() Clears the map, resetting the size to zero and nullifying references to avoid garbage collection issues.
boolean	containsKey(java.lang.Object key) Checks whether the map contains the specified key.
boolean	containsValue(java.lang.Object value) Checks whether the map contains the specified value.
java.util.Set	entrySet() Gets the entrySet view of the map.
boolean	equals(java.lang.Object obj) Compares this map with another.
java.lang.Object	get(java.lang.Object key) Gets the value mapped to the key specified.
int	hashCode() Gets the standard Map hashCode.
boolean	isEmpty() Checks whether the map is currently empty.
java.util.Set	keySet() Gets the keySet view of the map.
MapIterator	mapIterator() Gets an iterator over the map.
java.lang.Object	put(java.lang.Object key, java.lang.Object value) Puts a key-value mapping into this map.
void	putAll(java.util.Map map) Puts all the values from the specified map into this map.
java.lang.Object	remove(java.lang.Object key) Removes the specified mapping from this map.
int	size() Gets the size of the map.
java.lang.String	toString() Gets the map as a String.
java.util.Collection	values() Gets the values view of the map.

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Method Detail

get

public java.lang.Object get(java.lang.Object key)

Gets the value mapped to the key specified.

Specified by:

get in interface java.util.Map

Parameters:

key - the key

Returns:

the mapped value, null if no match

size

public int size()

Gets the size of the map.

Specified by:

size in interface java.util.Map

Returns:

the size

isEmpty

public boolean isEmpty()

Checks whether the map is currently empty.

Specified by:

isEmpty in interface java.util.Map

Returns:

true if the map is currently size zero

containsKey

public boolean containsKey(java.lang.Object key)

Checks whether the map contains the specified key.

Specified by:

containsKey in interface java.util.Map

Parameters:

key - the key to search for

Returns:

true if the map contains the key

containsValue

public boolean containsValue(java.lang.Object value)

Checks whether the map contains the specified value.

Specified by:

containsValue in interface java.util.Map

Parameters:

value - the value to search for

Returns:

true if the map contains the value

put

public java.lang.Object put(java.lang.Object key,
                            java.lang.Object value)

Puts a key-value mapping into this map.

Specified by:

put in interface java.util.Map

Parameters:

key - the key to add

value - the value to add

Returns:

the value previously mapped to this key, null if none

putAll

public void putAll(java.util.Map map)

Puts all the values from the specified map into this map.

Specified by:

putAll in interface java.util.Map

Parameters:

map - the map to add

Throws:

java.lang.NullPointerException - if the map is null

remove

public java.lang.Object remove(java.lang.Object key)

Removes the specified mapping from this map.

Specified by:

remove in interface java.util.Map

Parameters:

key - the mapping to remove

Returns:

the value mapped to the removed key, null if key not in map

clear

public void clear()

Clears the map, resetting the size to zero and nullifying references to avoid garbage collection issues.

Specified by:

clear in interface java.util.Map

mapIterator

public MapIterator mapIterator()

Gets an iterator over the map. Changes made to the iterator affect this map.

A MapIterator returns the keys in the map. It also provides convenient methods to get the key and value, and set the value. It avoids the need to create an entrySet/keySet/values object. It also avoids creating the Map.Entry object.

Specified by:

mapIterator in interface IterableMap

Returns:

the map iterator

entrySet

public java.util.Set entrySet()

Gets the entrySet view of the map. Changes made to the view affect this map. The Map Entry is not an independent object and changes as the iterator progresses. To simply iterate through the entries, use mapIterator().

Specified by:

entrySet in interface java.util.Map

Returns:

the entrySet view

keySet

public java.util.Set keySet()

Gets the keySet view of the map. Changes made to the view affect this map. To simply iterate through the keys, use mapIterator().

Specified by:

keySet in interface java.util.Map

Returns:

the keySet view

values

public java.util.Collection values()

Gets the values view of the map. Changes made to the view affect this map. To simply iterate through the values, use mapIterator().

Specified by:

values in interface java.util.Map

Returns:

the values view

equals

public boolean equals(java.lang.Object obj)

Compares this map with another.

Specified by:

equals in interface java.util.Map

Overrides:

equals in class java.lang.Object

Parameters:

obj - the object to compare to

Returns:

true if equal

hashCode

public int hashCode()

Gets the standard Map hashCode.

Specified by:

hashCode in interface java.util.Map

Overrides:

hashCode in class java.lang.Object

Returns:

the hash code defined in the Map interface

toString

public java.lang.String toString()

Gets the map as a String.

Overrides:

toString in class java.lang.Object

Returns:

a string version of the map